We are studying the roles of the liver, kidney, gastrointestinal tract, mammary gland and placenta in vitamin A metabolism of fetal sheep with various maternal intakes of vitamin A, and in neonatal lambs. We have determined significant differences in plasma retinol transport and clearance of retinol from plasma with varied vitamin A intake, a major fecal excretory route for vitamin A derivatives and significant increases in plasma lipid-soluble vitamin A metabolites with increasing vitamin A intake. While studying placental transport of retinol, we have determined a distinct and significant difference in fetal vitamin A metabolism. We are presently examining effect of maternal vitamin A intake on fetal retinol metabolism.